1. Field of the Invention
Example embodiments of the present invention relate to a method of inspecting defects and an apparatus for performing the same method, and more particularly, to a method of inspecting semiconductor processing defects, such as particles and scratches, and to an apparatus for performing the method.
A claim of priority is made to Korean Patent Application No. 2005-57450 filed on Jun. 30, 2005, the content of which is herein incorporated by reference in its entirety.
2. Description of the Related Art
The high integration degree and the high performance of semiconductor devices necessitate an inspection process for detecting various processing defects on a semiconductor wafer. As examples, processing defects include particles on a wafer, and bridge failures and structural collapses generated during patterning processes. As another example, processing defects include scratches generated on the surface of a wafer during a chemical mechanical polishing (CMP) process. A defect inspection process includes inspecting the processing defects and determining what effect the defects may have on a wafer in a subsequent process.
In general, defect inspection processes are largely classified into dark-field inspection processes based on a light scattering theory, and bright-field inspection processes based on a high-speed microscope theory. Both the conventional dark-field inspection process and the conventional bright-field inspection process compare image data to detect for processing defects, where the image data corresponds to dies on a semiconductor substrate. Neighboring dies adjacent to each other are required to be substantially identical on a semiconductor substrate. Therefore, differences between the image data of the neighboring dies indicate that processing defects exist in the neighboring dies on the substrate.
A die on a semiconductor substrate generally has a complicated structure, including a cell structure, a peripheral structure, a sense amplifier (SA) and a sub-word divider (SWD), and thus the neighboring dies on the substrate are difficult to compare with each other. As a result, comparison of the neighboring dies requires high-quality measurement equipment. In particular, both the conventional dark-field inspection process and the conventional bright-field inspection process require advanced optical equipment and calculation equipment.
FIG. 1 is a flow chart showing a conventional method of inspecting for processing defects. In particular, the flow chart in FIG. 1 shows an operational sequence for detecting processing defects on a wafer during a manufacturing process for a semiconductor device.
Referring to FIG. 1, an inspection wafer, which is randomly selected among to-be-inspected wafers, is loaded into a detection apparatus for detecting processing defects on the wafer (step S11), and a laser is irradiated onto the wafer (step S12). The irradiated laser is reflected from the wafer (step S13), and the reflected laser is focused into a photo multiplier tube (step S14). The photo multiplier tube calculates an optimal amplification ratio in accordance with an intensity of the reflected laser (step S15). The reflected laser is amplified in accordance with the optimal amplification ratio (step S16). The amplified laser is transformed into a digital signal (step S17), and the digital signal is stored into a server (step S18). Then, the digital signal is compared with a reference signal that is obtained from a reference wafer, and the detection apparatus provides information as to whether or not the inspection wafer includes a processing defect (step S19).
Various minute structures such as a line, a spacer, a contact hole and a pattern are formed on a corresponding region of a wafer such as a cell region, a peripheral region, an SA region and an SWD region. A reflectivity of the minute structure is substantially the same in the same region, but is different from that in another region. That is, the reflectivity of the minute structure is varied in accordance with each region of the wafer. Accordingly, when the reflection laser is amplified at the same amplification ratio regardless of each region of the wafer, the image data measured from each region of the wafer is also different from one another in accordance with each region of the wafer. As a result, the difference between the measured image data does not provide any information on the existence of the defect on the wafer. For the above reasons, high-quality and advanced optical equipment and calculation equipment are required for detecting processing defects using the comparison of the measured image data. Such high-quality and advanced optical equipment and calculation equipment are expensive, and generally a long time is needed to detect for processing defects. That is, a large amount of image data is compared with one another during the detection process, and as a result the conventional detection of processing defects consumes a lot of time even when sophisticated and expensive detection equipment is utilized.
Japanese Laid-Open Patent Publication 1997-203621 discloses a method of inspecting pattern defects, a method of evaluating a process for manufacturing a semiconductor using the same, and a method of adjusting positions of a plurality of image data. Japanese Laid-Open Patent Publication 1998-185535 discloses a system for manufacturing semiconductor devices and a method of inspecting processing defects.
According to the above patent publications, a light is irradiated onto an inspection wafer on which a unit process for manufacturing a semiconductor device is performed, and a reflected light reflected from the wafer is filtered and detected through a complicated optical unit. Image data regarding the inspection wafer is measured by processing the detected reflected light. The measured image data is differentiated with reference to time, and the differentiated imaged data is compared with reference image data. A plurality of actual wafers undergoes the same process as conducted on the inspection wafer, and the processing defects on the actual wafers are detected by naked-eye inspection equipment, such as a microscope and a scanning electron microscope (SEM). One of the actual wafers satisfying a given defect standard is selected as the reference wafer and the reference image data is obtained from the reference wafer.
The above patent publications, each of the measured image data is compared with the reference image data for detecting the processing defects and as a result, detection efficiency is not sufficiently improved. In addition, high cost equipment is utilized and a long time is need to obtain the reference image data.
In the past, only several tens of the processing defects were typically detected on a semiconductor wafer. More recently, however, several hundreds or several thousands of the processing defects are typically being detected on a semiconductor wafer due to the high integration degrees thereof. However, the development of inspection methods and apparatus has not been able to keep pace with that of the semiconductor device, so that the costs and time for detecting for processing defects, thus reducing manufacturing throughput.